T-Rex Predator or Scavenger?

T-rex has been assumed to be an active hunter since it was first discovered in 1905. Jack Horner has recently been challenging this assumption. He goes further than to suggest this animal might have scavenged, he says that this animals was never - and could never - have been an active hunter.

-Jack Horner suggests that useless little front limbs are a strong indication that T rex scavenged.

Crocodiles are the closest animal we know which can show the raw reptilian bite force that T rex must have been able to exert. Their jaw is their only weapon. Therefore T rex's small arms cannot rule out predatory behavior.

-Horner says that predatory animals must fight and jump and therefore might fall. If T rex fell it might break its jaw and ribs and could not recover, particularly without strong arms to cusion itsself.

Take other animals for instance - A fall can be fatal to a giraffe and yet they frequently run. Monkeys die falling from trees but it doesnt mean they stop climbing. There are many examples of how everyday life can be a potential death-trap.

The fossils record bears witness to the rough and dangerous life of large, theropod dinosaurs. The most famous and most complete T rex skeleton, Sue, has a broken fibula.

-By looking at the proportions of T rex legs Jack Horner shows that T rex was not a runner. It has a short fibia compared the femur. T rex couldnt eat what it couldnt catch.

This observation must be placed in context. The prey of T rex would have been other large animals. T rex only needed to be as fast as the animals upon which it fed, such as Edmontosaurus or Triceratops. Caculations have shown that, even without running, a 12m long T rex would easily reach 25 miles per hour. At good stride T rex could certainly match a Hadrosaur and possibly Triceratops.


-C.A.T. scans of T rex skulls show us the brain case and therefore, roughly, the shape of the brain. Jack Horner explains that Tyrannosaurs had a large olfactory lobe and a small optical system. He points out this is very similar in proportion to a vulture. Vultures use their keen sense of smell to scent dead meat over tens of miles and, if T rex had the same type of brain, then it too must have been a scavenger.

The brain of T rex was also very similar to another modern-day animal: The Alligator. Birds (including vultures) have an enlarged area of the brain devoted to processing data however alligators, like large theropod dinosaurs, have a smaller part of the brain developed to processing and a large portion devoted to just receiving sensory input. This doesnt tells us if the food was been sought out living or dead, but rather how the hunter reacts when it reaches it.

Out of all the large meat eating Theropod Dinosaurs T-rex brain was by far the biggest. Other Dinosaurs some that might have been even bigger then the T-Rex like the Giganatosaurs had a the part of the brain that produces intellgence that was 50% smaller then the T-Rex


Well if you couldnt tell im a supporter of T-rex as a Hunter. Dont get me wrong I think he did scavenge too. If you were another dinosaur and you just killed something and T-rex came along I think that was now T-rex's meal.

But I also think he was a active hunter. There is evidence of a T-rex bite to the tail of a Duckbill that broke a vertabrate off its tail. The interesting part of it is that the broken bone had healed meaning the Duckbill was alive during the attack. There is even new evidence comming to light that may prove T-rex lived in packs.


I think if you put all paleontologist that thought T-rex was a scavenger on one side of a stadium , and all the paleontologist that thought he was a hunter on the other side and then put a T-rex in the middle there wouldnt be very many people left to find out which he was.

So what does everyone think of the Tyrant lizard King Predator or Scavenger?







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The very design of the T-Rex shows it was an eating machine - an apex predator. While we can argue about the size of it's olfactory lobe and optics, the bones are what we have. It's much like the Great White or a salt-water crocodile. Those are both eating machines. The T-Rex didn't need strong arms when it had a jaw and neck that strong. I imagine it could run up to a hydrosaur, tilt its head to one side, grab a neck, and just thrash. I just can't imagine a monster that size being a scavenger. Nature has a niche for scavenger animals on Earth today and none of them are nearly as large as the planet's serious predators - it's just not efficient. Calling this thing a scavenger... it's like a far-future scientist looking at the bones of a Great White, a Bengal tiger, or Grizzly and saying they weren't hunters but scavengers.

Also I don't know about the pack idea. The reason is it would take an enormous amount of food to feed a pack of T-Rex, a pack of T-Rex could wreck the prey in an area fairly quickly. While these creatures weren't exactly reptiles they weren't exactly mammals either, so it's hard to say. But I'm willing to bet they had zones of control dominated by males and their families.

The very design of the T-Rex shows it was an eating machine - an apex predator.

Yep. I agree.

I'll disagree on the packing though. The female was much larger than the male, and they likely behaved more like small lion prides is my guess. Much like a gazelle etc. will feed a pack of lions, I'm betting the same was so for the T-Rex's prey.

I think he was both. I think if he would run across a dead animal he would eat it. He is for sure a Killer. The teeth are the true sign of this.

Well, no animal will turn down a free meal.... I'm sure T-Rex's routinely cheated other, smaller predators out of their kills too, but that doesn't make them any less a predator....

I think they were much like lions and crocs. They waited for their prey, saw a straggler, then surprise attack. Last I remember they were thought to run at a pretty good clip. Surely enough to catch a straggler of the herd.

the same pointless argument is brought up about great whites....does it matter ? a huge predator needs to eat, and eating carrion doesn't make it any less "scary"......as far as the latest theory, wasn't t-rex initially thought to stand upright with his tail on the ground ? we will never know the truth unless someone comes across enough amber with mosquitos in it.....

and according to the experts, bumble bees can't fly, they're wings are too short......

Originally posted by radagast
as far as the latest theory, wasn't t-rex initially thought to stand upright with his tail on the ground ? we will never know the truth unless someone comes across enough amber with mosquitos in it.....

and according to the experts, bumble bees can't fly, they're wings are too short......

Yeah the Peabody Museum near where I lived had the T-rex mounted like that along with many other museums. They were actually breaking the T-rex's back like in three places to mount it like that but I guess they thought it looked right back then as they really thought they were more reptile and most moderen reptiles drag their tails.

As for the pack thing the theory comes from two finds on a group of T-rexs that were all different ages and all died in the same area at about the same time. The first thought was that it was from a predator trap, a la the La Brea tar pits. But its seems there was no trap and that they seemed to have all died while in a group.

One theory is that different ages of T-rex had their own role in Hunting in a pack. The younger/teenage T-rexs which would be faster would herd a target animal into a ambush attack the waiting jaws of a large female.

Well - another interesting point to add on the pro-scavenger side would be that, as J. Horner also says:

...but so far no study has shown that tyrannosaurs killed other dinosaurs for food (a bone showing tyrannosaur tooth marks that had healed would be strong evidence for predation).
Source

Wasn't he featured on a National Geographic episode that dealt with the same question?

I can not think of any predator that is not also a scavager.

Animals dont put themselves into classes they eat whatever is handy usually prey that is very old or young, sick or wounded or already dead or dying.

I would have to say it was both

the pack question is much more interesting , imo, raptors I can see as pack hunters, a t-rex pack would proably make too much noice to be effective, and most pack hunters use the strategy to catch bigger or faster prey, and I think the t-rex is plenty big, how fast is also a good question, but I would make the analogy of a t-rex being like a polar bear or other apex predator.....and now for something completly different.....


did you read about the prostitute penguins ? the females mate with males who bring them stones for their nest while their real mate isn't around.....some males even tip with extra stones...too funny

Originally posted by EnronOutrunHomerun
Well - another interesting point to add on the pro-scavenger side would be that, as J. Horner also says:

...but so far no study has shown that tyrannosaurs killed other dinosaurs for food (a bone showing tyrannosaur tooth marks that had healed would be strong evidence for predation).
Source

Wasn't he featured on a National Geographic episode that dealt with the same question?

Yeah J. Horner has been on alot of shows since he has put this theory forward. Some of the shows are just his side of the story I really dont like those much. But then there are shows with him that will have other famous paleontologist like Bob Baker that disagree with him and they just kill his case and tend to go with the both Hunter/scavenger.

There is a case I saw on one of the shows with a Duckbill that had a T-Rex bite on its tail that had healed. Im looking for this info online and will post when I find it.

Horner says when he tells his theory to little kids in schools they throw stuff at him

[edit on 12-8-2004 by ShadowXIX]

Found it

Recently, Dr. Kenneth Carpenter (from the Denver Museum of Natural History) found a healed T. rex tooth mark on the tail of a hadrosaur (a duck-billed dinosaur). This is evidence that T. rex was an active predator, and not simply a scavenger. Why else would T. rex bite a duck-billed dinosaur?


www.enchantedlearning.com... diet.shtml

Still looking for a picture of it though

as far as the latest theory, wasn't t-rex initially thought to stand upright with his tail on the ground ?

Yep, but now we know that's all wrong. They got it right with "Sue" (one of the largest and most complete T-Rex's ever found). Got to see a cast of her at Disney not too long ago. The tail was held out above ground and used as a counter balance to the front-heavy T-Rex while running, much as the smaller running dinos are depicted.

Recently, Dr. Kenneth Carpenter (from the Denver Museum of Natural History) found a healed T. rex tooth mark on the tail of a hadrosaur (a duck-billed dinosaur). This is evidence that T. rex was an active predator, and not simply a scavenger. Why else would T. rex bite a duck-billed dinosaur?

Well, you know my position on it, but just to be Devil's advocate, the pro-scavenger camp would simply state that the T-Rex likely just bit it to drag it off, etc.

[edit on 12-8-2004 by Gazrok]

As has been mentioned before, just because T-Rex was a active predator, this does not exclude the fact that like ANY other predatory predator, they were scavengers also. A free meal was just as tasty as a meal one had to 'kill' for, forgive the pun.


seekerof

What was rather interesting about the wound, not only did we have this U shape groove but there was re-healed bone around it.

The bone could only have re-healed if the animal was alive, and if the animal was alive that made the T. rex a predator.

Thats what was so important about this find All other T-rex Teeth marks (Like those found on many Triceratops) according to Horner were that on already dead animal


I know your playing Devil's advocate


[edit on 12-8-2004 by ShadowXIX]

Here's an interesting find in a similar context - no healing for this poor dino tho...

Check out this website where I pulled it from: T-Rex No Vulture

The researchers determined that the ferocious beast could exert between 1,440 and 3,011 pounds of force, greater than the crushing force of any known creature though close to the maximum force exerted by the American alligator, a dinosaur relative.

"This is like the weight of a pickup truck behind each tooth," Erickson says. The estimate is for a bite during feeding, which typically is less forceful than higher velocity snapping bites such as those used by alligators to seize prey.

The new evidence appears to refute arguments made by some scientists that T-Rex was primarily a scavenger because its teeth were too weak to attack live prey.

Cool site thats a crazy amount of power in a bite. It would probablly just crush the spine of whatever it wanted.

I know there are Theropods that might have been bigger down in South America like Giganotsaurus. But its estimated jaw pressure was nowhere near that of the T-Rex which was like the pitbull in bite power of the Theropods.

Also when you look at the teeth of Giganotsaurus they are really more like knives sharp but thin they would snap if the ever bit into bone. Thr T-rex teeth on the other hand are better described as Armour piercing spikes made to dig right into and crush bone as your picture shows.

Originally posted by ShadowXIX


-Jack Horner suggests that useless little front limbs are a strong indication that T rex scavenged.

I recall a functional study was done not too long ago, the general conlusion of which seemed to be that the arms were good at absorbing shock and (and I might be stretching this abit) 'hodling' things. Not the hand itself, but the entire limb. I image this to mean its used as something like meat hooks, things that latch on when extremely close and prevent the prey from getting away. Obviously not something a scavanger would need, but also, not necessarily supporting an extremely active predator. It might in fact better support the idea of an ambush predator, something that bursts out of nowhere, locks hold of the prey, and dispatches it then.

Crocodiles are the closest animal we know which can show the raw reptilian bite force that T rex must have been able to exert.

Keep in mind that there were other dinosaurs that cna be studied also, in terms of jaw mechanics. Also, there are other living animals that have powerful jaws that can be studied, not only crocodiles.


-Horner says that predatory animals must fight and jump and therefore might fall. If T rex fell it might break its jaw and ribs and could not recover, particularly without strong arms to cusion itsself.

Take other animals for instance - A fall can be fatal to a giraffe and yet they frequently run.

Four legged animals are much much more stable than two legged ones, especiall dinosaurs. Humans have a spine as a central supporting column, dinosaurs, however, have to be balanced at their hip.

Monkeys die falling from trees but it doesnt mean they stop climbing.

they don't weight several tons either.

-By looking at the proportions of T rex legs Jack Horner shows that T rex was not a runner. It has a short fibia compared the femur. T rex couldnt eat what it couldnt catch.

This observation must be placed in context. The prey of T rex would have been other large animals. T rex only needed to be as fast as the animals upon which it fed, such as Edmontosaurus or Triceratops. Caculations have shown that, even without running, a 12m long T rex would easily reach 25 miles per hour. At good stride T rex could certainly match a Hadrosaur and possibly Triceratops.

The problem is that the T.Rex has a short fibia compared to the femur relative to other predatory dinosaurs, like allosaurus or ceratosaurus and the like. So this ratio is used to support the idea that it was slower compared to other dinosaurs, and why would they be so much faster if they didn't need to be?

The brain of T rex was also very similar to another modern-day animal: The Alligator. Birds (including vultures) have an enlarged area of the brain devoted to processing data however alligators, like large theropod dinosaurs, have a smaller part of the brain developed to processing and a large portion devoted to just receiving sensory input. This doesnt tells us if the food was been sought out living or dead, but rather how the hunter reacts when it reaches it.

The cat scan data shows that the t rex had an abnormally and particularly enlarged portion of the brain concerned with processing scent, on the order of the ratio that a vulture, a pure scavenger that 'hunts' thru scent, has. Aligators do not have the same proportions of the different parts of their brains.

Out of all the large meat eating Theropod Dinosaurs T-rex brain was by far the biggest. Other Dinosaurs some that might have been even bigger then the T-Rex like the Giganatosaurs had a the part of the brain that produces intellgence that was 50% smaller then the T-Rex

Horner wasn't talking about the part of the brain concerning 'intelligence', he was talking about the part involved in sense of smell. The large olfactory bulbs indicate that trex had an unusually powerful sense of smell.

Where did you get that information concerning relative brain sizes by the way?

Well if you couldnt tell im a supporter of T-rex as a Hunter

You probably can't tell from what i've been saying but I think he was a hunter too. I think that the olfactory information requires an explanation, and the unusual leg ratios indicate that something was going on with t rex that wasn't happeneing in other large predatory dinosaurs.

Some people in this thread, i have noticed, are missing that horner is adovacting that t rex was exclusively a scavenger. Just on the surface tho, there are very very few animals that do this. Vultures do it, but, a vulture has the advantage of being able to glide in the air under minimal muscle power and cover extraordinary distances from that vantage point. A t rex would have to walk to the carrion, which is a vastly different way of expending energy, and requires a good deal of time, time for other animals to get to the kill.

I did rather like the cgi animation of a t rex stomping up to a kill in the recent show about this. Even if dozens of other animals beat the t rex to the kill, they certainly aren't going to stand in its way.

Lions, from what I understand, often do this.

[edit on 13-8-2004 by Nygdan]

perhaps there is more to the equation that we simple do not or will not ever know. While the T-Rex is basicly a giant running mouth with ill suited limbs perhaps there is more, chameleon skin, venomous bite, electric discharge or some sophisticated communication system like the ULF sounds elephants use that amde them the uber killer, none of these would ever show up on a fossil.

Interesting idea Apollyon I always loved the Dilophosaurus as spitting venom and with the frill around the neck in Jurassic Park movie thought that was pretty cool.

I sometimes wonder if there is whole classes of animals we will never know about because they didnt have bones like dinosaurs or mammals perhaps using some form of cartilage like a shark does but without even the the bone jaws and teeth. Seeing that the teeth and jaws are all we find of the huge Megladon.

Perhaps one day will find a T-Rex in a undreamed of state of preservation due to some freak accident.Maybe a baby T-Rex caught in amber like bugs are sometimes. I wont hold my breath but I can hope